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101.
This study was carried out to examine the effects of the meiosis-activating C(29) sterol, 4,4-dimethyl-5 alpha-cholesta-8,14, 24-trien-3 beta-ol (FF-MAS), on mouse oocyte maturation in vitro. Cumulus cell-enclosed oocytes (CEO) and denuded oocytes (DO) from hormonally primed, immature mice were cultured 17-18 h in minimum essential medium (MEM) containing 4 mM hypoxanthine plus increasing concentrations of FF-MAS. The sterol induced maturation in DO with an optimal concentration of 3 microg/ml but was without effect in CEO, even at concentrations as high as 10 microg/ml. Some stimulation of maturation in hypoxanthine-arrested CEO was observed when MEM was replaced by MEMalpha. Interestingly, the sterol suppressed the maturation of hypoxanthine-arrested CEO in MEM upon removal of glucose from the medium. FF-MAS also failed to induce maturation in DO when meiotic arrest was maintained with dibutyryl cAMP (dbcAMP). The rate of maturation in FF-MAS-stimulated, hypoxanthine-arrested DO was slow, as more than 6 h of culture elapsed before significant meiotic induction was observed, and this response required the continued presence of the sterol. Although the oocyte took up radiolabeled lanosterol, such accumulation was restricted by the presence of cumulus cells. In addition, lanosterol failed to augment FSH-induced maturation and was even inhibitory at a high concentration. Moreover, the downstream metabolite, cholesterol, augmented the inhibitory action of dbcAMP on maturation in both CEO and DO. Two inhibitors of 14 alpha-demethylase, ketoconazole, and 14 alpha-ethyl-5 alpha-cholest-7-ene-3 beta, 15 alpha-diol that can suppress FF-MAS production from lanosterol failed to block consistently FSH-induced maturation. These results confirm the stimulatory action of FF-MAS on hypoxanthine-arrested DO but do not support a universal meiosis-inducing function for this sterol. 相似文献
102.
103.
Ruan B Wilson WK Pang J Gerst N Pinkerton FD Tsai J Kelley RI Whitby FG Milewicz DM Garbern J Schroepfer GJ 《Journal of lipid research》2001,42(5):799-812
Smith-Lemli-Opitz syndrome (SLOS) is a hereditary disorder in which a defective gene encoding 7-dehydrocholesterol reductase causes the accumulation of noncholesterol sterols, such as 7- and 8-dehydrocholesterol. Using rigorous analytical methods in conjunction with a large collection of authentic standards, we unequivocally identified numerous noncholesterol sterols in 6 normal and 17 SLOS blood samples. Plasma or erythrocytes were saponified under oxygen-free conditions, followed by multiple chromatographic separations. Individual sterols were identified and quantitated by high performance liquid chromatography (HPLC), Ag(+)-HPLC, gas chromatography (GC), GC-mass spectrometry, and nuclear magnetic resonance. As a percentage of total sterol content, the major C(27) sterols observed in the SLOS blood samples were cholesterol (12;-98%), 7-dehydrocholesterol (0.4;-44%), 8-dehydrocholesterol (0.5;-22%), and cholesta-5,7,9(11)-trien-3beta-ol (0.02;-5%), whereas the normal blood samples contained <0.03% each of the three noncholesterol sterols. SLOS and normal blood contained similar amounts of lathosterol (0.05;-0.6%) and cholestanol (0.1;-0.4%) and approximately 0.003;-0.1% each of the Delta(8), Delta(8(14)), Delta(5,8(14)), Delta(5,24), Delta(6,8), Delta(6,8(14)), and Delta(7,24) sterols.The results are consistent with the hypothesis that the Delta(8(14)) sterol is an intermediate of cholesterol synthesis and indicate the existence of undescribed aberrant pathways that may explain the formation of the Delta(5,7,9(11)) sterol. 19-Norcholesta-5,7,9-trien-3beta-ol was absent in both SLOS and normal blood, although it was routinely observed as a GC artifact in fractions containing 8-dehydrocholesterol. The overall findings advance the understanding of SLOS and provide a methodological model for studying other metabolic disorders of cholesterol synthesis. 相似文献
104.
The impact of pH and calcium on the uptake of fluoride by tea plants (Camellia sinensis L.) 总被引:6,自引:0,他引:6
BACKGROUND AND AIMS: Tea plants (Camellia sinensis L.) accumulate large amounts of fluoride (F) from soils containing normal F concentrations. The present experiments examined the effects of pH and Ca on F uptake by this accumulating plant species. METHODS: The effect of pH was assessed in two experiments, one using uptake solutions with different pHs, and the other using lime, as CaO, applied to the soil. The effect of Ca was examined by analysing F concentrations in plants supplied with varying amounts of Ca, as Ca(NO3)2, either in uptake solutions or through the soil. KEY RESULTS: F uptake was highest at solution pH 5.5, and significantly lower at pH 4.0. In the soil experiment, leaf F decreased linearly with the amounts of lime, which raised the soil pH progressively from 4.32 to 4.91, 5.43, 5.89 and, finally, 6.55. Liming increased the water-soluble F content of the soil. Including Ca in the uptake solution or adding Ca to soil significantly decreased leaf F concentrations. The distribution pattern of F in tea plants was not altered by Ca treatment, with most F being allocated to leaves. The activity of F- in the uptake solution was unaffected and water-soluble F in the soil was sometimes increased by added Ca. CONCLUSIONS: F uptake by tea plants, which are inherently able to accumulate large quantities of F, was affected both by pH and by Ca levels in the medium. The reduced F uptake following Ca application appeared not to be due simply to the precipitation of CaF2 in solution and soil or to the complexing of Ca and F in roots, although these factors cannot be dismissed. It was more likely due to the effect of Ca on the properties of cell wall or membrane permeability in the solution experiments, and to alteration of F speciations and their quantities in soil solutions following Ca application. 相似文献
105.
Optimal HIV treatment by maximising immune response 总被引:1,自引:1,他引:0
We present an optimal control model of drug treatment of the human immunodeficiency virus (HIV). Our model is based upon ordinary differential equations that describe the interaction between HIV and the specific immune response as measured by levels of natural killer cells. We establish stability results for the model. We approach the treatment problem by posing it as an optimal control problem in which we maximise the benefit based on levels of healthy CD4+ T cells and immune response cells, less the systemic cost of chemotherapy. We completely characterise the optimal control and compute a numerical solution of the optimality system via analytic continuation.Research supported by the Natural Science and Engineering Research Council (NSERC) and the Mathematics of Information Technology and Complex Systems (MITACS) of Canada 相似文献
106.
Ruan Z Koizumi T Sakai A Ishizaki T Wang Z Chen Q Wang X 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2004,174(7):549-554
To compare the role of nitric oxide in an adaptive process to chronic hypoxia, we examined the effects of endogenous nitric oxide synthase inhibition on pulmonary vascular tone in conscious sheep and pigs living at high altitude. Unanesthetized male sheep (n=6) and pigs (n=5), born and residing in the highlands of Qinghai Province, China (2,300–3,000 m a.s.l.) were studied at that altitude. Pulmonary artery pressure (Ppa), pulmonary artery wedge pressure (Pcwp), and cardiac output (CO) were measured. Pulmonary vascular resistance (PVR) was calculated as (Ppa—Pcwp)/CO. Using a climatic chamber, hemodynamic measurements during exposures to atmospheric pressures corresponding to altitudes of 0, 2,300, and 4,500 m a.s.l. were performed with and without NO inhibition, using Nw-nitro-l-argine (NLA; 20 mg kg–1), a potent stereospecific competitive inhibitor of nitric oxide synthase. Ppa and PVR at baseline (2,300 m) and during hypoxic exposure (4,500 m) were significantly higher in pigs than in sheep. After NLA administration, Ppa increased and CO decreased in both animals, resulting in significantly increased PVR at baseline and during hypoxic exposure. However, there were no significant differences in the percent increase in basal or hypoxic PVR after NLA administration between sheep and pigs. We conclude that augmented endogenous NO production could contribute to the regulation of pulmonary vascular tone at high altitude in sheep and pigs. However, it is unlikely that NO is responsible for the different pulmonary vascular tones between sheep and pigs at basal condition at moderately high altitude.Communicated by G. Heldmaier 相似文献
107.
Detection of tumor marker CA125 in ovarian carcinoma using quantum dots 总被引:11,自引:0,他引:11
The fluorescent labeling of biological materials usingsmall-molecule organic dyes is widely employed in bio-logical imaging and clinical diagnosis. Organic fluoro-phores, however, have certain characteristics that limittheir advantages in some applications. These limitationsinclude narrow excitation bands and broad emissionbands with red spectral tails, which make the simultaneousevaluation of several light-emitting probes difficult due tospectral overlap. Also, many organic dyes exhibit highp… 相似文献
108.
Silva MD Savinainen A Kapadia R Ruan J Siebert E Avitahl N Mosher R Anderson K Jaffee B Schopf L Chandra S 《Molecular imaging》2004,3(4):312-318
Micro-computed tomographic (micro-CT) imaging provides a unique opportunity to capture 3-D architectural information in bone samples. In this study of pathological joint changes in a rat model of adjuvant-induced arthritis (AA), quantitative analysis of bone volume and roughness were performed by micro-CT imaging and compared with histopathology methods and paw swelling measurement. Micro-CT imaging of excised rat hind paws (n = 10) stored in formalin consisted of approximately 600 30-mum slices acquired on a 512 x 512 image matrix with isotropic resolution. Following imaging, the joints were scored from H&E stained sections for cartilage/bone erosion, pannus development, inflammation, and synovial hyperplasia. From micro-CT images, quantitative analysis of absolute bone volumes and bone roughness was performed. Bone erosion in the rat AA model is substantial, leading to a significant decline in tarsal volume (27%). The result of the custom bone roughness measurement indicated a 55% increase in surface roughness. Histological and paw volume analyses also demonstrated severe arthritic disease as compared to controls. Statistical analyses indicate correlations among bone volume, roughness, histology, and paw volume. These data demonstrate that the destructive progression of disease in a rat AA model can be quantified using 3-D micro-CT image analysis, which allows assessment of arthritic disease status and efficacy of experimental therapeutic agents. 相似文献
109.
Ruan W Lindner E Langosch D 《Protein science : a publication of the Protein Society》2004,13(2):555-559
An oligo-leucine sequence has previously been shown to function as an artificial transmembrane segment that efficiently self-assembles in membranes and in detergent solution. Here, a novel technique, asparagine-scanning mutagenesis, was applied to probe the interface of the self-assembled oligo-leucine domain. This novel approach identifies interfacial residues whose exchange to asparagine leads to enhanced self-interaction of transmembrane helices by interhelical hydrogen bond formation. As analyzed by the ToxR system in membranes, the interface formed by the oligo-leucine domain is based on a leucine-zipper-like heptad repeat pattern of amino acids. In general, the strongest impacts on self-assembly were seen with asparagines located around the center of the sequence, indicating that interaction is be more efficient here than at the termini of the transmembrane domains. 相似文献
110.
We consider a two-dimensional model of cell-to-cell spread of HIV-1 in tissue cultures, assuming that infection is spread
directly from infected cells to healthy cells and neglecting the effects of free virus. The intracellular incubation period
is modeled by a gamma distribution and the model is a system of two differential equations with distributed delay, which includes
the differential equations model with a discrete delay and the ordinary differential equations model as special cases. We
study the stability in all three types of models. It is shown that the ODE model is globally stable while both delay models
exhibit Hopf bifurcations by using the (average) delay as a bifurcation parameter. The results indicate that, differing from
the cell-to-free virus spread models, the cell-to-cell spread models can produce infective oscillations in typical tissue
culture parameter regimes and the latently infected cells are instrumental in sustaining the infection. Our delayed cell-to-cell
models may be applicable to study other types of viral infections such as human T-cell leukaemia virus type 1 (HTLV-1).
Received: 18 November 2000 /
Published online: 28 February 2003
RID="*"
ID="*" Research was partially supported by the NSERC and MITACS of Canada and a start-up fund from the College of Arts and
Sciences at the University of Miami. On leave from Dalhousie University, Halifax, Nova Scotia, Canada.
Current address: Department of Mathematics, Clarke College, Dubuque, Iowa 52001, USA
Key words or phrases: HIV-1 – Cell-to-cell spread – Time delay – Stability – Hopf bifurcation – Periodicity 相似文献